Seattle, WA Environmental Rules: Boat Dock Permits (2026)

Boat dock construction and modification in Seattle is regulated under multiple jurisdictions. The Seattle Shoreline Master Program (SMC 23.60A) requires a Shoreline Substantial Development Permit for new docks, significant expansions, or replacements within the shoreline district. Routine maintenance of existing docks may qualify for a shoreline exemption from SDCI. All dock projects must be evaluated for environmental impact, particularly regarding salmon habitat, eelgrass beds, and water quality. The SMP limits overwater coverage and requires the use of materials and designs that minimize shading of aquatic habitat, such as grating and light-penetrating surfaces. The U.S. Army Corps of Engineers requires a Section 10 permit under the Rivers and Harbors Act for any structure in navigable waters, and a Section 404 permit under the Clean Water Act for any fill in waters of the United States. The Washington Department of Ecology may require a Hydraulic Project Approval (HPA) from the Department of Fish and Wildlife for work affecting fish habitat. Dock design must comply with navigation safety standards. In Lake Union, Lake Washington, and the Ship Canal, additional regulations may apply regarding vessel moorage and liveaboard restrictions.